Whilst the primary focus of absorbent articles remains the ability of these articles to absorb and retain fluids, another important area of development in this field is the control of odourous compounds contained within the absorbed fluids or their degradation products. There are a wide range of compounds which may be present in an absorbent article during use which result in the formation of malodourous. These compounds include fatty acids, ammonia, amines, sulphur containing compounds and ketones and aldehydes.
The art is replete with descriptions of various odour controlling agents for use in absorbent articles in order to address the problem of malodour formation. These agents can typically be classified according to the type of odour the agent is intended to combat. Odours may be classified as being acidic, basic or neutral. Acidic odour controlling agents have a pH greater than 7 and typically include inorganic carbonates, bicarbonates, phosphates and sulphates. Basic odour controlling agents have a pH of less than 7 and include compounds such as citric acid, boric acid and maleic acid.
Neutral odour controlling agents have a pH of approximately 7. Examples of these types of compounds include activated carbons, clays, zeolites, silicas and starches. Such neutral odour controlling agents are the most commonly utilised in absorbent articles.
For example EPO 348 978 discloses an absorbent article comprising an odour control system wherein the neutral odour controlling particles are selected from carbon, clays, silicas, zeolites and molecular sieves. EPO 510 619 relates to absorbent article comprising odour control complex including a combination of at least 2 agents selected form a group which includes zeolites and silica gels. Similarly, WO 91/12029, WO 91/11977 and WO 91/12030 disclose the combination of zeolites and absorbent gelling materials.
EPO 282 287 discloses a deodouriser suitable for use in a sanitary napkin which is non black comprising at least one compound selected from metal silicates and metal salts of aluminum containing silicates selected from certain transition metals and group II metals.
WO 81/01643 relates to the removal of nitrogenous irritants present in waste matter in diapers by the use of an inorganic aluminosilicate zeolite ammonium ion exchange material. In addition silica gel may be present to absorb additional water. Carbon is a preferred component of the system
Carbon has been noted in the art as being particularly effective over a broad spectrum of odours. However, it is not favoured due to its black appearance, which is considered unacceptable by consumers. Hence a currently preferred odour control agent is zeolite particularly the so-called intermediate and high ratio zeolites. Although zeolite does not have a negative aesthetic profile, its main drawback is its lack of effective odour control over a broad range of odour types and the expense of such materials.
Consequently, there still exists a need to provide an odour controlling agent or system which has an acceptable aesthetic profile such that it is light coloured and provides effective odour control over a wide range of malodourous compounds and which is not expensive.
It has now been observed that this need may be addressed by the use of the combination of zeolite with silica to effectively combat a wide range of odours which may be present within an absorbent article. Furthermore, the wide range odour control benefits are provided by a dual component system not a tri component system.
An additional advantage of the present invention is that the odour control system comprises components which are all light in colour and thus are not noticeable within the absorbent article and are therefore acceptable from a consumer standpoint.
None of the identified prior art has recognised that this specific combination of absorbent gelling materials and silica provides the above described benefits.